Fig 3. Phylogenetic tree comparing sequences of chikungunya virus strains from Puerto Rico with strains from other regions.

Sequences (700 bp) from the E1 envelope glycoprotein gene were aligned and compared in a neighbor-joining tree with a Jukes-Cantor model and 1000 bootstrapping replicates. The resulting tree, with GenBank accession numbers, was displayed by using FigTree v1.2 (http://tree.bio.ed.ac.uk/software/figtree/). The scale bar indicates the distance corresponding with 0.01 nucleotide substitutions per site.